U.S. patent number 7,555,927 [Application Number 11/577,471] was granted by the patent office on 2009-07-07 for bottle-shaped can manufacturing method and bottle-shaped can.
This patent grant is currently assigned to Universal Can Corporation. Invention is credited to Tatsuya Hanafusa, Takashi Hasegawa, Masahiro Hosoi, Ryoichi Ito.
United States Patent |
7,555,927 |
Hanafusa , et al. |
July 7, 2009 |
Bottle-shaped can manufacturing method and bottle-shaped can
Abstract
In a bottle-shaped can manufacturing method and a bottle-shaped
can, a necking process is performed on an opening portion of a
cylindrical workpiece with a bottom several times to form a body, a
shoulder, and a portion for forming a neck that is continuously
connected to an upper end of the shoulder in the axial direction of
the bottle-shaped can and extends upward, and a first convex is
formed in at least one of a connection portion between the shoulder
and the portion for forming the neck and a connection portion
between the shoulder and the body. Then, the shoulder is pressed to
the inside of the body while the first convex is recessed inward in
the radial direction, thereby forming grooves in the shoulder.
Inventors: |
Hanafusa; Tatsuya (Gotenba,
JP), Ito; Ryoichi (Gotenba, JP), Hosoi;
Masahiro (Gotenba, JP), Hasegawa; Takashi
(Sunto-gun, JP) |
Assignee: |
Universal Can Corporation
(Tokyo, JP)
|
Family
ID: |
36202773 |
Appl.
No.: |
11/577,471 |
Filed: |
March 11, 2005 |
PCT
Filed: |
March 11, 2005 |
PCT No.: |
PCT/JP2005/004327 |
371(c)(1),(2),(4) Date: |
April 18, 2007 |
PCT
Pub. No.: |
WO2006/043347 |
PCT
Pub. Date: |
April 27, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080069665 A1 |
Mar 20, 2008 |
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Foreign Application Priority Data
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Oct 20, 2004 [JP] |
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2004-305533 |
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Current U.S.
Class: |
72/349; 72/715;
72/379.4 |
Current CPC
Class: |
B21D
51/2615 (20130101); B65D 1/0223 (20130101); Y10S
72/715 (20130101) |
Current International
Class: |
B21D
22/26 (20060101); B21D 51/00 (20060101) |
Field of
Search: |
;72/348,349,379.4,715,405.03,97 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2000-515072 |
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Nov 2000 |
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JP |
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2004-123231 |
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Apr 2004 |
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JP |
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2004123231 |
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Apr 2004 |
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JP |
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2004-250063 |
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Sep 2004 |
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JP |
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Other References
International Search Report for PCT/JP2005/004327 mailed May 10,
2005. cited by other.
|
Primary Examiner: Ross; Dana
Assistant Examiner: Sullivan; Debra M
Attorney, Agent or Firm: Darby & Darby P.C.
Claims
The invention claimed is:
1. A method of manufacturing a bottle-shaped can including a body
having a large diameter, a shoulder that is continuously connected
to an upper end of the body in an axial direction of the body and
is tapered upward, a neck that is continuously connected to an
upper end of the shoulder in the axial direction and extends
upward, and a cap that is engaged with a male screw formed on the
neck, comprising: performing a necking process on an opening
portion of a cylindrical workpiece with a bottom and the body
several times to form the body, the shoulder, and a portion for
forming the neck that is continuously connected to the upper end of
the shoulder in the axial direction and extends upward; forming a
first convex in at least one of a connection portion between the
shoulder and the portion for forming the neck and a connection
portion between the shoulder and the body such that the first
convex protrudes outward in a radial direction from the entire
circumference of the connection portion; pressing a line linking
the upper end to a lower end of the shoulder in a direction in
which the shoulder is inclined to an inside of the bottle-shaped
can to form, in a circumferential direction of the shoulder, a
plurality of grooves extending in an inclined direction; pressing a
lower end of the line with a mold surface having a triangular
shape, with one vertex of the triangular mold surface disposed at
the lower end of the line; and pressing a point on the line where
the first convex is disposed to be recessed inward in the radial
direction.
2. The method of manufacturing a bottle-shaped can in accordance
with claim 1, wherein the first convex is formed in the connection
portion between the shoulder and the portion for forming the neck,
and the line links the recessed portion of the first convex to the
portion pressed by the one vertex of the triangular mold surface in
the direction in which the shoulder is inclined.
3. The method of manufacturing a bottle-shaped can in accordance
with claim 1, wherein after the shoulder and the portion for
forming the neck are formed, pressing a portion from the upper end
of the shoulder to the lower end of the portion for forming the
neck inward in the radial direction such that the width of the
portion is reduced, thereby forming the first convex in the
connection portion between the shoulder and the portion for forming
the neck, and pressing the shoulder to the inside of the body while
the first convex is being pressed inward in the radial direction,
thereby forming the grooves.
4. The method for manufacturing a bottle-shaped can in accordance
with claim 1, wherein a cylindrical mold having an inner
circumferential surface that is formed substantially in the same
shape as that of the shoulder and a plurality of pressure portions,
each extending substantially in the inclined direction of the
shoulder, that are formed in the circumferential direction on the
inner circumferential surface so as to protrude inward in the
radial direction is arranged so as to coaxially face the opening
portion of the cylindrical workpiece with the bottom, and moving
the mold and the cylindrical workpiece with the bottom close to
each other in the axial direction of the cylindrical workpiece with
the bottom such that the opening portion of the cylindrical
workpiece with the bottom is inserted into the mold and the
pressure portions are pressed against the shoulder, thereby forming
in the circumferential direction the plurality of grooves
satisfying the following Expression: L1=h/cos .alpha.,
a1=2rsin(360.degree./(2n)), a2=2sin(360.degree./(2n))(r-htan
.alpha.), L2=a2L1/(a1-a2), and .theta.=2arc sin(a2/2L), wherein L1:
the length of the shoulder in the inclined direction, a1: the width
of a lower end of the groove in the axial direction of the
bottle-shaped can, a2: the width of an upper end of the groove in
the axial direction of the bottle-shaped can, L2: the distance
between the upper end of the shoulder in the axial direction of the
bottle-shaped can and an intersection point between two extension
lines of both ends of the groove in the circumferential direction
that extend upward in the axial direction of the bottle-shaped can,
n: the number of grooves (8.ltoreq.n.ltoreq.22), r: the radius of
an outer circumferential surface of the body, h: the length of the
shoulder in the axial direction of the bottle-shaped can, and
.alpha.: an angle formed between the axis of the bottle-shaped can
and the outer circumferential surface of the shoulder, and .theta.:
an angle formed by extending the two ends of the groove upward in
the axial direction.
5. The method of manufacturing a bottle-shaped can in accordance
with claim 1, wherein after the grooves are formed, performing a
drawing process on a part of the portion for forming the neck other
than the lower end in the axial direction to reduce the diameter of
the part, thereby forming a second convex protruding outward in the
radial direction at the lower end in the axial direction, the lower
end in the axial direction being a part of the portion for forming
the neck.
6. The method of manufacturing a bottle-shaped can in accordance
with claim 1, wherein after the first convex is formed, performing
a drawing process on a part of the portion for forming the neck
other than the lower end in the axial direction to reduce the
diameter of the part, thereby forming a second convex protruding
outward in the radial direction at the lower end in the axial
direction, the lower end in the axial direction being a part of the
portion for forming the neck, and thereafter the grooves are
formed.
7. The method of manufacturing a bottle-shaped can in accordance
with claim 1, wherein the grooves are formed under the condition
that an internal pressure of the bottle-shaped can is in the range
of 0.05 MPa to 0.70 MPa.
8. A bottle-shaped can comprising: a body that has a large
diameter; a shoulder that is continuously connected to an upper end
of the body in an axial direction of the body and is tapered
upward; a neck that is continuously connected to an upper end of
the shoulder in the axial direction and extends upward; and a cap
that is engaged with a male screw formed on the neck, wherein the
bottle-shaped can is formed by the bottle-shaped can manufacturing
method in accordance with to claim 1, a portion of a groove other
than a lower end in a direction in which the shoulder is inclined
is formed in a V shape in sectional view in a direction orthogonal
to the axis of the bottle-shaped can, the lower end of the groove
in an inclined direction has a triangular shape as viewed from the
outside in a radial direction, and one of three vertexes of the
triangle is disposed at an upper end in the inclined direction and
a lower end of the V-shaped bottom in the inclined direction, and
the remaining two vertexes are disposed at both ends of a lower end
of the shoulder in the inclined direction.
Description
CROSS REFERENCE TO PRIOR APPLICATIONS
This is a U.S. national phase application under 35 U.S.C. .sctn.371
of International Patent Application No. PCT/JP2005/004327, filed
Mar. 11, 2005, and claims benefit of Japanese Patent Application
No. 2004-305533, filed on Oct. 20, 2004, both of them are
incorporated by reference in its entirety. The International
Application was published in Japanese on Apr. 27, 2006 as
International Publication No. WO/2006/043347 under PCT Article
21(2).
FIELD OF THE INVENTION
The present invention relates to a bottle-shaped can manufacturing
method and a bottle-shaped can.
BACKGROUND
In general, aluminum cans have been used to contain beverages.
However, in recent years, bottle-shaped cans with screw caps have
been proposed. In general, the bottle-shaped can includes a large
body, a shoulder whose diameter gradually decreases from a lower
end to an upper end of the body, and a neck extending from the
upper end of the shoulder upward, and a cap is engaged with a male
screw formed on the neck.
The bottle-shaped can is formed by performing a DI process on a
metal plate to form a cylindrical workpiece with a bottom,
performing a necking process on an opening portion of the
cylindrical workpiece several times to form a body, a shoulder, and
a portion for forming a neck that is continuously connected to an
upper end of the shoulder and extends upward, and performing, for
example, a drawing process, a screw shaping process, and a curl
forming process on the cylindrical workpiece.
In recent years, in order to appeal to consumers, this type of
bottle-shaped can has needed to be changed so as to have various
shapes with a high-quality design. In the related art, for example,
printing or emboss processing has been used to manufacture the
bottle-shaped can. The emboss process is disclosed in, for example,
in JP-A-2004-123231 and JP-T-2000-515072.
JP-A-2004-123231 discloses the following method: a cylindrical mold
having an inner circumferential surface that is formed
substantially in the same shape as that of a shoulder, and a
plurality of pressure portions, each extending substantially in the
inclined direction of the shoulder, that are formed in the
circumferential direction on the inner circumferential surface so
as to protrude inward in the radial direction is arranged so as to
coaxially face the opening portion of a cylindrical workpiece with
the bottom; and, the mold and the cylindrical workpiece with the
bottom are moved close to each other in the axial direction of the
cylindrical workpiece with the bottom such that the opening portion
of the cylindrical workpiece with the bottom is inserted into the
mold and the pressure portions are pressed against the shoulder,
thereby forming in the circumferential direction the plurality of
grooves extending in the inclined direction of the shoulder.
JP-T-2000-515072 discloses the following method a first rotating
body and a second rotating body are supported such that they can be
rotated on their rotational axes parallel to each other; the first
rotating body is arranged inside a cylindrical workpiece with a
bottom and the second rotating body is arranged outside the
cylindrical workpiece with a bottom; and the first and second
rotating bodies are moved close to each other and are rotated on
their rotational axes, with a body of the cylindrical workpiece
interposed between outer circumferential portions of the first and
second rotating bodies, thereby performing emboss processing on the
body (forming convex and concave portions).
In the manufacturing method disclosed in JP-T-2000-515072, since
the emboss processing is performed with the inner and outer
circumferential surfaces of the body interposed between the first
and second rotating bodies, it is possible to accurately form the
concave and convex portions in the body. That is, when the body is
interposed between the outer circumferential portions of the first
and second rotating bodies, the convex portions formed in the outer
circumferential surface of the second rotating body in the axial
direction are fitted into the concave portions formed in the outer
circumferential surface of the first rotating body in the axial
direction with the body interposed therebetween. That is, metal
forming the body is prevented from flowing in the circumferential
direction, and the body is recessed inward in the radial direction.
Therefore, the convex portions on the second rotating body can be
accurately transferred onto the body.
However, in the manufacturing method disclosed in JP-A-2004-123231,
the pressure portions of the mold are only pressed against the
outer circumferential surface of the shoulder, but no pressure is
applied to the inner circumferential surface of the shoulder, which
makes it difficult to accurately form the grooves. That is, when
the pressure portions of the mold are pressed against only the
outer circumferential surface of the shoulder without pressing the
inner circumferential surface of the shoulder, metal flow occurs in
the shoulder in both the circumferential direction and the axial
direction, which causes both portions of the shoulder pressed by
the pressure portions and peripheral portions to be recessed to the
inside of the body. As a result, it is difficult to form grooves
having steep side walls in the outer circumferential surface of the
shoulder and thus for the groove to be clearly viewed.
In order to solve the above-mentioned problems, the manufacturing
method disclosed in JP-T-2000-515072 has been proposed in which a
mold is also arranged inside the shoulder, and the shoulder is
interposed between the mold provided inside the shoulder and a mold
for pressing the outer circumferential surface of the shoulder.
However, as described above, in a bottle-shaped can having a body,
a shoulder that is connected to an upper end of the body and is
tapered upward, and a neck that has a small diameter and extends
from the upper end of the shoulder upward, it is difficult to
arrange the mold inside the shoulder, and thus it is difficult to
use this manufacturing method for this type of bottle-shaped
can.
SUMMARY OF THE INVENTION
The present invention provides a bottle-shaped can capable of
appealing to consumers and a method of accurately manufacturing the
bottle-shaped can.
According to an aspect of the invention, there is provided a method
of manufacturing a bottle-shaped can including a body having a
large diameter, a shoulder that is continuously connected to an
upper end of the body in an axial direction of the body and is
tapered upward, a neck that is continuously connected to an upper
end of the shoulder in the axial direction and extends upward, and
a cap that is engaged with a male screw formed on the neck. The
method includes: performing a necking process on an opening portion
of a cylindrical workpiece with a bottom and the body several times
to form the body, the shoulder, and a portion for forming the neck
that is continuously connected to the upper end of the shoulder in
the axial direction and extends upward; forming a first convex in
at least one of a connection portion between the shoulder and the
portion for forming the neck and a connection portion between the
shoulder and the body such that the first convex protrudes outward
in a radial direction from the entire circumference of the
connection portion; pressing a line linking the upper end to the
lower end of the shoulder in a direction in which the shoulder is
inclined to the inside of the body to form, in a circumferential
direction of the shoulder, a plurality of grooves extending in the
inclined direction; pressing a lower end of the line with a mold
surface having a triangular shape, with one vertex of the
triangular mold surface disposed at the lower end of the line; and
pressing a point on the line where the first convex is disposed to
be recessed inward in the radial direction.
In this structure, since the first convex is recessed inward in the
radial direction to form the grooves, it is possible to prevent
portions of the first convex that are not pressed from being
recessed inward in the radial direction due to the deformation of
the first convex recessed inward in the radial direction. That is,
it is possible to make the portions of the first convex that are
not recessed have resistance to pressure applied to the inside of
the bottle-shaped can, that is, a protruding force toward the
outside of the bottle-shaped can in the radial direction. In this
way, it is possible to manufacture a bottle-shaped can having
grooves with steep side walls in the outer circumferential surface
of the shoulder. As a result, it is possible to improve the quality
of design of the bottle-shaped can.
When the grooves are formed, the first convex can prevent metal
forming at least one of the body and the portion for forming the
neck from flowing to the shoulder or into the grooves, which makes
it possible to form the grooves having a large depth and to prevent
at least one of the portions for forming the neck and the body from
being wrinkled.
Further, since the triangular mold surface is pressed against the
lower end of the shoulder to form the grooves, it is possible to
reliably prevent the body from being wrinkled.
Further, since the line of the shoulder is pressed to form the
groove, it is possible to form grooves in the shoulder in a
straight line in the inclined direction of the shoulder.
In this way, it is possible to form a bottle-shaped can having a
high-quality design.
Furthermore, instead of this structure, a necking process may be
performed on an opening portion of a cylindrical workpiece with a
bottom and a body several times to form the body, the shoulder, and
a portion for forming a neck that is continuous with an upper end
of the shoulder in the axial direction of the cylindrical workpiece
and extends upward, and a thick portion protruding outward from the
body may be formed in at least one of the upper end and the lower
end of the shoulder. As such, the thick portion of the shoulder may
be pressed to the inside of the body to form grooves extending in a
direction in which the shoulder is inclined.
The first convex may be formed in the connection portion between
the shoulder and the portion for forming the neck, and the line may
link the recessed portion of the first convex to the portion
pressed by the one vertex of the triangular mold surface in the
direction in which the shoulder is inclined.
According to the above-mentioned structure, it is possible to
reliably form grooves extending in the direction in which the
shoulder is inclined.
After the shoulder and the portion for forming the neck are formed,
a portion from the upper end of the shoulder to the lower end of
the portion for forming the neck may be pressed inward in the
radial direction such that the width of the portion is reduced,
thereby forming the first convex in the connection portion between
the shoulder and the portion for forming the neck. As such, the
shoulder may be pressed to the inside of the body while the first
convex is being pressed inward in the radial direction, thereby
forming the grooves.
According to the above-mentioned structure, since the first convex
is pressed inward in the radial direction to form the grooves in
the circumferential direction of the shoulder, it is possible to
easily form the grooves without lowering the roundness of the neck.
That is, the first convex is formed after theneckingg process.
Therefore, even when the roundness of the portion for forming the
neck is lowered due to the necking process, it is possible to
correct the lowered roundness and thus to prevent the lowering of
the roundness of the portion for forming the neck.
When the first convex is pressed to the inside of the body,
relatively low pressure is applied to the shoulder, starting from
the recessed first convex, so that the groove is formed from the
upper end to the lower end of the shoulder in the inclined
direction. For example, when the cylindrical workpiece with the
bottom is formed by a DI process, it is possible to easily and
accurately form the grooves and to prevent the body from being bent
when the grooves are formed, due to the alignment of metal crystals
of the cylindrical workpiece W formed by the DI process.
A cylindrical mold having an inner circumferential surface that is
formed substantially in the same shape as that of the shoulder and
a plurality of pressure portions, each extending substantially in
the inclined direction of the shoulder, that are formed in the
circumferential direction on the inner circumferential surface so
as to protrude inward in the radial direction may be arranged so as
to coaxially face the opening portion of the cylindrical workpiece
with the bottom. Then, the mold and the cylindrical workpiece with
the bottom may be moved close to each other in the axial direction
of the cylindrical workpiece with the bottom such that the opening
portion of the cylindrical workpiece with the bottom is inserted
into the mold and the pressure portions are pressed against the
shoulder, thereby forming in the circumferential direction the
plurality of grooves satisfying the following Expression: L1=h/cos
.alpha., a1=2rsin(360.degree./(2n)),
a2=2sin(360.degree./(2n))(r-htan .alpha.), L2=a2L1/(a1-a2), and
.theta.=2a sin(a2/2L),
where L1: the length of the shoulder in the inclined direction,
a1: the width of a lower end of the groove in the axial direction
of the bottle-shaped can,
a2: the width of an upper end of the groove in the axial direction
of the bottle-shaped can,
L2: the distance between the upper end of the shoulder in the axial
direction of the bottle-shaped can and an intersection point
between two extension lines of both ends of the groove in the
circumferential direction that extend upward in the axial direction
of the bottle-shaped can,
n: the number of grooves (8.ltoreq.n.ltoreq.22),
r: the radius of an outer circumferential surface of the body,
h: the length of the shoulder in the axial direction of the
bottle-shaped can, and
.alpha.: an angle formed between the axis of the bottle-shaped can
and the outer circumferential surface of the shoulder.
According to the above-mentioned structure, since the groove is
formed so as to satisfy the above-mentioned Expression, it is
possible to reliably form a bottle-shaped can having a high-quality
design.
That is, when the number of grooves is larger than 22, the gap
between adjacent pressure portions is reduced in the mold, and a
change in the shape of the shoulder is limited by the pressure
portions when the grooves are formed, which makes it difficult to
appropriately adjust the depth and length of the groove (in the
direction in which the shoulder is inclined). On the other hand,
when the number of grooves is smaller than 8, the groove shape is
not formed, which makes it difficult to form a bottle-shaped can
having a high-quality design.
After the grooves are formed, a drawing process may be performed on
a part of the portion for forming the neck other than the lower end
in the axial direction to reduce the diameter of the part, thereby
forming a second convex protruding outward in the radial direction
at the lower end of the portion for forming the necking the axial
direction.
According to the above-mentioned structure, after the grooves are
formed, the second convex is formed, which makes it possible to
correct the roundness of the portion for forming the neck even when
the roundness of the portion for forming the neck is lowered due to
the formed grooves.
After the first convex is formed, a drawing process may be
performed on a part of the portion for forming the neck other than
the lower end in the axial direction to reduce the diameter of the
part, thereby forming a second convex protruding outward in the
radial direction at the lower end of the portion for forming the
necking the axial direction, and thereafter the grooves are
formed.
According to the above-mentioned structure, since the second convex
is formed before the grooves are formed, it is possible to improve
the rigidity of the portion for forming the neck against pressure
applied when the grooves are formed, and to prevent the roundness
of the portion for forming the neck from being lowered when the
grooves are formed. In addition, even when pressure applied to the
shoulder is transmitted to the portion for forming the neck during
the formation of the grooves, the second convex makes it possible
to prevent the portion for forming the neck from being wrinkled due
to the transmitted pressure.
The grooves may be formed under the condition such that the
internal pressure of the bottle-shaped can is in the range of 0.05
MPa to 0.70 MPa.
According to the above-mentioned structure, it is possible to
prevent the body from being bent.
According to another aspect of the invention, a bottle-shaped can
includes: a body that has a large diameter; a shoulder that is
continuously connected to an upper end of the body in an axial
direction of the body and is tapered upward; a neck that is
continuously connected to an upper end of the shoulder in the axial
direction and extends upward; and a cap that is engaged with a male
screw formed on the neck. The bottle-shaped can is formed by the
above-mentioned bottle-shaped can manufacturing method. A portion
of the groove other than the lower end in the direction in which
the shoulder is inclined is formed in a V shape in sectional view
in a direction orthogonal to the axis of the bottle-shaped can, and
the lower end of the groove in the inclined direction has a
triangular shape as viewed from the outside in a radial direction.
In addition, one of three vertexes of the triangle is disposed at
an upper end in the inclined direction and a lower end of the
V-shaped bottom in the inclined direction, and the remaining two
vertexes are disposed at both ends of the lower end of the shoulder
in the inclined direction.
According to the above-mentioned structure, since the grooves
formed in the outer circumferential surface of the shoulder each
have steep side walls, the grooves can be clearly viewed, which
makes it possible to provide a bottle-shaped can having a
high-quality design.
In the above-mentioned bottle-shaped can manufacturing method, a
bottle-shaped can manufacturing apparatus including a holding
portion for holding the bottom of the cylindrical workpiece and a
tool holding portion having a plurality of shaping tools for
forming the cylindrical workpiece into various shapes may be
prepared. Then, the manufacturing apparatus may sequentially
perform various processes on the cylindrical workpiece with the
bottom by using the shaping tools to form a bottle-shaped can. In
this case, a cylindrical mold having an inner circumferential
surface that is formed substantially in the same shape as that of
the shoulder and a plurality of pressure portions, each extending
substantially in the inclined direction of the shoulder, that are
formed in the circumferential direction on the inner
circumferential surface so as to protrude inward in the radial
direction is provided as one of the shaping tools. The mold is
arranged so as to coaxially face the opening portion of the
cylindrical workpiece with the bottom, and the mold and the
cylindrical workpiece with the bottom are moved close to each other
in the axial direction of the cylindrical workpiece with the bottom
such that the opening portion of the cylindrical workpiece with the
bottom is inserted into the mold and the pressure portions are
pressed against the shoulder, thereby forming the grooves.
According to the above-mentioned structure, it is possible to form
the plurality of grooves on the entire circumferential surface of
the shoulder at once and thus to improve productivity. In addition,
since a uniform load can be applied to the entire circumferential
surface of the shoulder, it is possible to minimize a reduction in
the roundness of the portion for forming the neck.
According to the above-described aspects of the invention, it is
possible to provide a bottle-shaped can having a high-quality
design.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A to 1D are partial sectional side views illustrating an
opening portion of a cylindrical workpiece with a bottom in various
processes of a bottle-shaped can manufacturing method according to
an embodiment of the invention.
FIG. 2 is a side view illustrating a bottle-shaped can manufactured
by the bottle-shaped can manufacturing method according to an
embodiment of the invention.
FIG. 3 is an enlarged sectional view illustrating a portion of a
groove shown in FIG. 2.
FIG. 4 is a partial perspective view illustrating the bottle-shaped
can shown in FIG. 2.
FIG. 5 is a table illustrating the dimensions of portions of the
bottle-shaped can shown in FIG. 4.
FIG. 6 is a side view illustrating a bottle-shaped can
manufacturing apparatus for performing the bottle-shaped can
manufacturing method shown in FIG. 1.
FIG. 7 is a cross-sectional view taken along the line X1-X1 of FIG.
6 showing the bottle-shaped can manufacturing apparatus.
FIG. 8 is a plan view illustrating a groove forming mold, which is
one of the shaping tools provided in a tool holding portion shown
in FIG. 6.
FIG. 9 is a cross-sectional view taken along the line X2-X2 of FIG.
8 showing the groove forming mold.
FIG. 10 is a cross-sectional view taken along the line X3-X3 of
FIG. 9 showing the groove forming mold.
FIG. 11 is a partial sectional side view illustrating an opening
portion of a cylindrical workpiece with a bottom after a first
process of a bottle-shaped can manufacturing method according to
another embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
Hereinafter, exemplary embodiments of the invention will be
described with reference to the accompanying drawings. However, the
invention is not limited to the following embodiments, and
components of the embodiments may be combined with each other.
First, a bottle-shaped can 1 to be formed will be described with
reference to FIG. 2.
The bottle-shaped can 1 is formed of, for example, aluminum or
aluminum alloy, and includes a body 2 having a large diameter, a
shoulder 3 that is connected to the upper end of the body 2 in the
axial direction of the bottle-shaped can and is tapered upward, and
a neck 4 that is connected to the upper end of the shoulder 3 in
the axial direction of the bottle-shaped can and extends upward. A
male screw portion 5 is formed on the neck 4, and a cap (not shown)
is engaged with the male screw portion 5.
Further, a protruding portion 6 protruding in the radial direction
is continuous with the lower end of the male screw portion 5 in the
axial direction of the bottle-shaped can. The protruding portion 6
includes a large-diameter portion whose diameter increases
downward, a top portion, which is a convex portion in the radial
direction, and a tapered portion whose diameter decreases downward,
which are formed in this order from the top to the bottom of the
protruding portion 6. A small-diameter portion 8 is continuous with
a lower end of the tapered portion having a small diameter in the
axial direction of the bottle-shaped can, and a second convex
portion 7 having a smaller diameter than the protruding portion 6
is continuous with a lower end of the small-diameter portion 8.
The upper end of the neck 4 in the axial direction of the
bottle-shaped can is a curl portion 9 that is bent in the radial
direction. In this way, the neck 4 has the curl portion 9, the male
screw portion 5, the protruding portion 6, the small-diameter
portion 8, and the second convex 7 formed in this order from the
top to the bottom thereof in the axial direction of the
bottle-shaped can. The neck 4 is smoothly connected to the shoulder
3 through the second convex 7.
A plurality of grooves 10 extending in a direction in which the
shoulder 3 is inclined are formed in the shoulder 3 in the
circumferential direction that is continuous with the lower end of
the second convex 7 in the axial direction of the bottle-shaped
can. As shown in FIG. 3, the groove 10 according to this embodiment
extends in the direction in which the shoulder 3 is inclined, and
the width (the size in the circumferential direction) of the groove
10 gradually increases from the upper end to the lower end thereof
in the inclined direction.
In addition, the groove 10 includes an upper end 10d, a lower end
10e, a bottom portion 10b recessed in the radial direction, and two
side walls 10a that extend from both sides of the bottom portion
10b in the circumferential direction and protrude to the outside in
the radial direction. In this way, a portion of the shoulder 3 in
the inclined direction thereof other than the upper end 10d and the
lower end 10e has a V shape in sectional view that is orthogonal to
the axis of the bottle-shaped can. Therefore, the plurality of
grooves 10 are connected to each other in the circumferential
direction of the shoulder 3 through their top portions 10c
protruding toward the outside in the radial direction.
The upper end 10d of the groove 10 is inclined such that the depth
E thereof gradually decreases upward, and the lower end 10e of the
groove 10 is inclined such that the depth E thereof gradually
decreases downward. That is, the displacement of the upper end 10d
of the groove 10 gradually increases downward, and the displacement
of the lower end 10e of the groove 10 gradually increases
upward.
As shown in FIGS. 2 and 4, the lower end 10e of the groove 10 has a
triangular shape in side view, as viewed from the outside in the
radial direction, and the triangular shape has three vertexes 10f,
10g, and 10h. Among the three vertexes, the vertex 10f is disposed
at the top of the triangle in the inclined direction and is also
disposed at the lower end of the V-shaped bottom portion 10b in the
inclined direction, and the two vertexes 10g and 10h are disposed
at both sides of the triangle in the circumferential direction of
the shoulder 3.
The groove 10 having the above-mentioned structure is formed such
that the size thereof shown in FIG. 4 satisfies the following
Expression: L1=h/cos .alpha., a1=2rsin(360.degree./(2n)),
a2=2sin(360.degree./(2n))(r-htan .alpha.), L2=a2L1/(a1-a2), and
.theta.=2a sin(a2/2L)
where L1: the length of the shoulder 3 in the inclined
direction,
a1: the width of a lower end of the groove 10 in the axial
direction of the bottle-shaped can,
a2: the width of an upper end of the groove 10 in the axial
direction of the bottle-shaped can,
L2: distance between the upper end of the shoulder 3 in the axial
direction of the bottle-shaped can and an intersection point K
between two extension lines of both ends (the top portions 10c) of
the groove in the circumferential direction that extend upward in
the axial direction of the bottle-shaped can,
n: the number of grooves (8.ltoreq.n.ltoreq.22),
r: the radius of the outer circumferential surface of the body
2,
h: the length of the shoulder 3 in the axial direction of the
bottle-shaped can, and
.alpha.: an angle formed between the axis of the bottle-shaped can
and the outer circumferential surface of the shoulder 3.
FIG. 5 shows the values of L1, a1, a2, L2, and .theta. calculated
by the above-mentioned Expression according to the number of
grooves 10. As shown in FIG. 3, the depth E of the groove 10, that
is, the distance E between the outer surface of the top portion 10c
and the outer surface of the bottom portion 10b in a direction
orthogonal to the inclined direction of the shoulder 3 is in the
range of 0.1 mm to 4.0 mm. The curvature radius of the outer
surface of the top portion 10c is in the range of 0.13 mm to 0.80
mm, and the curvature radius of the outer surface of the bottom
portion 10b is in the range of 0.13 mm to 0.80 mm. In addition, the
thicknesses of the side wall 10a, the bottom portion 10b, and the
top portion 10c of the groove 10 are in the range of 0.1 mm to 0.25
mm.
In the bottle-shaped can 1 in which the distance H from the
intersection point K to the top end of the shoulder 3 in the axial
direction is about 38.6 mm, the length h of the shoulder 3 in the
axial direction is about 22.75 mm, the angle .theta. formed between
the axis of the bottle-shaped can and the outer circumferential
surface of the shoulder 3 is about 28.degree., and the number of
grooves 10 is 14, an angle .theta.1 (see FIG. 3) between the outer
circumferential surfaces of the side walls 10a adjacent to each
other in the circumferential direction in the groove 10 that is at
a distance of 43 mm from the intersection point K downward in the
axial direction of the bottle-shaped can is 161.degree.. The angle
.theta.1 between the outer circumferential surfaces of the side
walls 10a in the groove 10 that is at a distance of 50 mm from the
intersection point K downward in the axial direction of the
bottle-shaped can is 166.degree.. The angle .theta.1 between the
outer circumferential surfaces of the side walls 10a in the groove
10 that is at a distance of 53 mm from the intersection point K
downward in the axial direction of the bottle-shaped can is
165.degree.. The angle .theta.1 between the outer circumferential
surfaces of the side walls 10a in the groove 10 that is at a
distance of 55 mm from the intersection point K downward in the
axial direction of the bottle-shaped can is 166.degree..
In the bottle-shaped can 1, an angle .theta.2 (see FIG. 3) between
the inner circumferential surfaces of the side walls 10a adjacent
to each other in the circumferential direction in the groove 10
that is at a distance of 43 mm from the intersection point K
downward in the axial direction of the bottle-shaped can is
140.degree.. The angle .theta.2 between the inner circumferential
surfaces of the side walls 10a in the groove 10 that is at
distances of 50 mm, 53 mm, and 55 mm from the intersection point K
downward in the axial direction of the bottle-shaped can is
144.degree..
In the bottle-shaped can 1 in which the distance H from the
intersection point K to the top end of the shoulder 3 in the axial
direction is about 38.6 mm, the length h of the shoulder 3 in the
axial direction is about 22.75 mm, the angle .alpha. formed between
the axis of the bottle-shaped can and the outer circumferential
surface of the shoulder 3 is about 28.degree., and the number of
grooves 10 is 16, the angle .theta.1 between the outer
circumferential surfaces of the side walls 10a in the groove 10
that is at a distance of 43.2 mm from the intersection point K
downward in the axial direction of the bottle-shaped can is
159.degree.. The angle .theta.1 between the outer circumferential
surfaces of the side walls 10a in the groove 10 that is at
distances of 50.2 mm, 53.2 mm, and 55.2 mm from the intersection
point K downward in the axial direction of the bottle-shaped can is
162.degree..
In this bottle-shaped can 1, the angle .theta.2 between the inner
circumferential surfaces of the side walls 10a in the groove 10
that is at a distance of 43.2 mm from the intersection point K
downward in the axial direction of the bottle-shaped can is
141.degree.. The angle .theta.2 between the inner circumferential
surfaces of the side walls 10a in the groove 10 that is at
distances of 50.2 mm and 53.2 mm from the intersection point K
downward in the axial direction of the bottle-shaped can is
144.degree.. The angle .theta.2 between the inner circumferential
surfaces of the side walls 10a in the groove 10 that is at a
distance of 55.2 mm from the intersection point K downward in the
axial direction of the bottle-shaped can is 143.degree..
As can be seen from the results, the angles .theta.1 and .theta.2
of the groove 10 are maintained at substantially constant values
over the overall length of the shoulder 3 in the inclined
direction.
Next, a method of manufacturing the bottle-shaped can 1 having the
above-mentioned structure will be described. In FIG. 6, a
bottle-shaped can manufacturing apparatus 20 includes a workpiece
holding portion 30 for holding a cylindrical workpiece W having a
bottom, a tool holding portion 40 that holds a shaping tool 42 for
shaping the cylindrical workpiece W having a bottom, and a driving
unit 22 for driving the two holding portions 30 and 40. The holding
portions 30 and 40 are arranged such that a workpiece holding
surface for holding the cylindrical workpiece W faces a tool
holding surface for holding the shaping tool 42. The cylindrical
workpiece W having the bottom is formed by performing a DI process
on a metal plate.
As shown in FIG. 7, in the workpiece holding portion 30, a
plurality of holding members 32 for holding the cylindrical
workpiece W are arranged in a circularshape on the surface of a
disk 31 supported by a shaft 21 that faces the tool holding portion
40. When the disk 31 is intermittently rotated by the driving unit
22, the cylindrical workpiece W having the bottom is supplied to
the holding member 32 from a supply portion 33, and the formed
bottle-shaped cans 1 are sequentially discharged from a discharge
portion 34. The holding member 32 holds a portion of the
cylindrical workpiece W from the bottom to a lower part of the body
in the axial direction of the cylindrical workpiece. In addition,
not all of the plurality of holding members 32 provided in the
circumference of the disk 31 are shown in FIG. 7, but some of them
are shown in FIG. 7.
In the tool holding portion 40, a plurality of various types of
shaping tools 42 are arranged in a circular shape on the surface of
a disk 41 supported by a shaft 21 that faces the workpiece holding
portion 30. The disk 41 is configured to move in the axial
direction of the shaft 21 by the driving unit 22. The tool holding
portion 40 is provided with a plurality of shaping tools 42 for
performing various shaping processes, such as a plurality of
drawing molds for reducing the diameter of an opening portion of
the cylindrical workpiece W having the bottom (a necking process),
a groove forming mold 50, which will be described later, for
forming the grooves 10 in the shoulder 3, a screw forming tool for
forming the male screw portion 5 on the neck 4, and a curl forming
tool for forming the curl portion 9 at the end of the opening
portion, and these shaping tools 42 are arranged in a circular
shape on the disk 41 in the order of processes.
When the tool holding portion 40 is moved to the left side of FIG.
6, the cylindrical workpieces W held by the workpiece holding
portion 30 are processed by the shaping tools 42.
The workpiece holding portion 30 (the disk 31) is intermittently
rotated on the shaft 21 such that the axes of the cylindrical
workpieces W with opening portions facing the tool holding portion
40 are identical with the central axes of the individual shaping
tools 42. When the disk 31 is intermittently rotated by the driving
unit 22, each cylindrical workpiece W having the bottom is moved to
a position opposite to the next shaping tool 42, and is then
processed by the shaping tool 42.
That is, when the tool holding portion 40 is moved close to the
workpiece holding portion 30, the cylindrical workpieces W each
having the bottom are processed by the corresponding shaping tools
42. When the tool holding portion 40 is separated from the
workpiece holding portion 30, the workpiece holding portion 30 is
rotated such that the shaping tools 42 for the next processes face
the cylindrical workpieces W. In this way, the approach/separation
of the tool holding portion 40 to/from the workpiece holding
portion 30 and the rotation of the workpiece holding portion 30 are
repeatedly performed to form the shoulder 3, the neck 4, and the
grooves 10 in the cylindrical workpiece W having the bottom,
thereby manufacturing the bottle-shaped can 1.
As shown in FIGS. 8 and 9, a groove forming mold 50 is formed in a
cylindrical shape, and the inner surface of the groove forming mold
50 includes an inner circumferential portion 53 that extends from
one end 51 of the mold 50 to the other end 52 substantially in
parallel to the central axis of the groove forming mold 50 and a
taper portion 54 whose diameter gradually increases from the one
end 51 to the other end 52.
The inner circumferential portion 53 and the taper portion 54 are
connected to each other such that the surface of the inner
circumferential portion 53 opposite to the one end 51 and the
surface of the taper portion 54 opposite to the other end 52 have
the same axis. In addition, the inner diameter of the taper portion
54 opposite to the other end 52 is substantially equal to the inner
diameter of the inner circumferential portion 53 opposite to the
one end 51.
The taper portion 54 has substantially the same shape as the
shoulder 3. As shown in FIGS. 8 and 10, a plurality of pressure
portions 55 that protrude inward in the radial direction and extend
in the inclined direction are formed on the surface of the taper
portion 54 at predetermined gaps in the circumferential
direction.
As shown in FIGS. 8 and 10, the pressure portion 55 is formed in a
triangular shape in a sectional view orthogonal to the axis line of
the groove forming mold 50. One side of the triangle forms a
circumferential surface of the taper portion 54, and the remaining
two sides are ascending wall surfaces 55d ascending inward from the
circumferential surface in the radial direction of the mold 50. An
intersection between the wall surfaces 55d is a top portion 55a of
the pressure portion 55.
A concave portion 56 is provided between the pressure portions 55
adjacent to each other in the circumferential direction. An end of
the pressure portion 55 (a mold surface; hereinafter, referred to
as a leading end 55b) disposed at the other end 52 of the mold 50
is inclined from the circumferential surface of the taper portion
54 of the mold 50 toward the one end 51. That is, the height of the
leading end 55b of the pressure portion 55 gradually decreases
toward the other end 52 of the mold 50. The leading end 55b has a
triangular shape in plan view as viewed from the axial direction of
the groove forming mold 50, and among three vertexes of the
triangle, two vertexes are disposed at the other end 52 of the
groove forming mold 50.
The other end of the pressure portion 55 (hereinafter, referred to
as a rear end 55c) disposed at the one end 51 of the mold 50 is
inclined from the circumferential surface of the taper portion 54
of the mold 50 toward the other end 52. That is, the height of the
rear end 55c of the pressure portion 55 gradually decreases toward
the one end 51 of the mold 50. The rear end 55c has a triangular
shape in plan view as viewed from the axial direction of the groove
forming mold 50, and among three vertexes of the triangle, two
vertexes are disposed at the one end 51 of the groove forming mold
50.
Further, the height of the pressure portion 55 protruding from the
circumferential surface of the taper portion 54 gradually decreases
from the leading end 55b to the rear end 55c. An angle between the
two ascending wall surfaces 55d forming the pressure portion 55 and
an angle between the ascending wall surfaces 55d, opposite to each
other, of the pressure portions adjacent to each other in the
circumferential direction of the taper portion 54 gradually
increase from the one end 51 of the mold 50 toward the other end
52.
In the above-mentioned structure, as described above, the tool
holding portion 40 is moved toward the workpiece holding portion,
with the one end 51 of the groove forming mold 50 held by the
surface of the tool holding portion 40 (the disk 41) and the other
end 52 facing the opening portion of the cylindrical workpiece W
having the bottom. Then, the opening portion of the cylindrical
workpiece W having the bottom is inserted into the mold 50 through
the other end 52 in the taper portion 54, and the entire surface of
the pressure portion 55 including the top portion 55a, the leading
end 55b, and the rear end 55c is pressed against the shoulder 3 to
form the grooves 10.
Next, a method of manufacturing the bottle-shaped can 1 shown in
FIGS. 2 and 3 by using the bottle-shaped can manufacturing
apparatus 20 having the above-mentioned structure will be described
below.
First, as shown in FIG. 7, the cylindrical workpiece W having the
bottom is supplied to the holding member 32 by the supply portion
33 and is then held by the holding member 32. Then, the disk 31 is
intermittently rotated such that the cylindrical workpiece W faces
one shaping tool 42 provided on the tool holding portion 40.
Subsequently, the intermittent rotation of the disk 31 and the
forward/backward movement of the tool holding portion 40 are
repeated to perform a necking process on the opening portion of the
cylindrical workpiece W having the bottom several times (for
example, 20 times), thereby gradually reducing the diameter of the
opening portion. In this way, the body 2, the shoulder 3, and a
portion 4a for forming the neck 4, which is continuous with the
upper end of the shoulder 3 in the axial direction of the
cylindrical workpiece W and extends in the vertical direction, are
formed.
Thereafter, pressure is applied to a portion from the lower end of
the portion 4a to the upper end of the shoulder 3 inward in the
radial direction at a position A shown in FIG. 7 to reduce the
diameter of that portion, thereby forming a first convex 11 (see
FIG. 1A) protruding outward in the radial direction along the
entire circumference of a connection portion between the shoulder 3
and the portion 4a. That is, the first convex 11, which is a thick
portion, protruding outward from the body of the bottle-shaped can
(outward in the radial direction) is formed at the upper end of the
shoulder 3. The thick portion means a portion of the shoulder 3 on
which a relatively large amount of metal is concentrated. For
example, the thickness of the thick portion is larger than the
average thickness of the shoulder portion 3.
The first convex 11 shown in FIG. 1A protrudes from both the
shoulder 3 and the portion 4a for forming the neck formed in the
radial direction.
Then, the disk 31 is rotated to dispose the cylindrical workpiece W
having the bottom at a position B that faces the groove forming
mold 50 shown in FIG. 7. Subsequently, the tool holding portion 40
is moved toward the disk 31, with the internal pressure of the
cylindrical workpiece W kept in the range of 0.05 MPa to 0.70 MPa,
to insert the portion 4a for forming the neckingto the groove
forming mold 50 from the other end 52. Then, the rear ends 55c of
the pressure portions 55 formed in the taper portion 54 press the
first convex 11 provided along the entire circumference toward the
inside of the shoulder 3, so that the first convex 11 is recessed
in the radial direction in a plurality of places that are at
predetermined intervals in the circumferential direction. In this
way, a plurality of grooves 10 extending in the inclined direction
of the shoulder 3 are formed in the circumferential direction (see
FIG 1B).
The lower end 10e of the groove 10 is formed by the leading end 55b
of the pressure portion 55, and the upper end 10d of the groove 10
is formed by the rear end 55c of the pressure portion 55. In
addition, the side wall 10a of the groove 10 is formed by the
ascending wall surface 55d of the pressure portion 55, and the
bottom portion 10b of the groove 10 is formed by the top portion
55a of the pressure portion 55.
The first convex 11 is recessed inward in the radial direction by
the rear end 55c of the pressure portion 55 and the one end 51 of
the top portion 55a of the top portion 55a of the pressure portion
55, and is also pressed to the inside of the cylindrical workpiece
by the leading end 55b having a triangular shape in plan view, with
the lower end of the shoulder 3 disposed at a top vertex of the
triangle (an intersection ridgeline between the leading end 55b and
the top portion 55a). In addition, among portions of the shoulder 3
other than the lower end, a line linking the recessed portion of
the first convex 11 to the portion pressed by the one vertex of the
leading end 55b is pressed by the top portion 55a to be recessed to
the inside of the cylindrical workpiece, thereby forming the groove
10.
At this point, the line of the shoulder 3 is recessed by the top
portion 55a, and a portion adjacent to the recessed portion in the
circumferential direction is pressed to the inside of the
cylindrical workpiece by the ascending side wall 55d such that the
width of the recessed portion increases in the circumferential
direction.
Then, after the disk 31 is rotated by a predetermined angle, the
tool holding portion 40 is moved toward the workpiece holding
portion 30 to perform a drawing process on a part of the portion 4a
other than the lower end in the axial direction of the cylindrical
workpiece, thereby reducing the diameter of the part. In this way,
a second convex 7 that protrudes outward in the radial direction
and is smoothly connected to the shoulder 3 is formed at the lower
end of the portion 4a in the axial direction of the cylindrical
workpiece (see FIG. 1C). Next, similarly, after the disk 31 is
rotated by a predetermined angle, the tool holding portion 40 is
moved toward the workpiece holding portion 30 to increase the
diameter of a part (hereinafter, referred to as a `large-diameter
portion`) of the portion 4a other than a portion of the second
convex 7 extending from the upper end to the lower end in the axial
direction of the cylindrical workpiece by a predetermined length,
thereby forming the small-diameter portion 8 and a small-diameter
portion of the protruding portion 6 (see FIG. 1D).
Similarly, after the disk 31 is rotated by a predetermined angle,
the tool holding portion 40 is moved toward the workpiece holding
portion 30 to reduce the diameter of a part of the large-diameter
portion other than the lower end in the axial direction of the
cylindrical workpiece, thereby forming the lower end of the
large-diameter portion in the protruding portion 6. Then, for
example, a screw forming process, a trimming process, and a curl
forming process are sequentially performed on the cylindrical
workpiece W having the bottom while repeating the intermittent
rotation of the disk 31, thereby forming the bottle-shaped can 1
shown in FIG. 2. Then, the bottle-shaped can 1 is discharged from
the bottle-shaped can manufacturing apparatus 20 by the discharge
portion 34 shown in FIG. 7, and is then carried to the next
stage.
As described above, according to the bottle-shaped can
manufacturing method of this embodiment, the shoulder 3 is pressed
to the inside of the cylindrical workpiece while the first convex
11 is recessed inward in the radial direction to form the groove
10. Therefore, it is possible to prevent a portion of the first
convex 11 that is not recessed by the rear end 55c of the pressure
portion 55 (the top portion 10c) from being recessed inward in the
radial direction due to the deformation of the first convex 11
recessed inward in the radial direction (the side wall 10a and the
bottom portion 10b).
That is, it is possible to make the portion of the first convex 11
that is not recessed (the top portion 10c) have resistance to
pressure applied to the inside of the bottle-shaped can, that is, a
protruding force toward the outside of the bottle-shaped can in the
radial direction. In this way, it is possible to manufacture the
bottle-shaped can 1 having the grooves 10 that are formed in the
outer circumferential surface of the shoulder 3 in the concave
shapes such that they are clearly viewed. As a result, it is
possible to improve the quality of design of the bottle-shaped can
1.
Further, since the first convex 11 is pressed inward in the radial
direction to form the grooves 10 in the shoulder 3, it is possible
to easily form the grooves 10 without lowering the roundness of the
neck 4. That is, in this embodiment, the first convex 11 is formed
after a necking process. Therefore, even when the roundness of the
portion 4a for forming the neck is lowered due to the necking
process, it is possible to correct the lowered roundness and thus
to prevent the lowering of the roundness of the portion 4a.
When the first convex 11 is pressed to the inside of the
cylindrical workpiece, relatively low pressure is applied to the
shoulder 30, starting from the recessed first convex 11, so that
the groove 10 is formed from the upper end to the lower end of the
shoulder 3 in the inclined direction. That is, it is possible to
easily and accurately form the groove 10 and to prevent the body 2
from being bent when the groove 10 is formed, due to the alignment
of metal crystals of the cylindrical workpiece W formed by a DI
process.
When the groove 10 is formed, the first convex 11 can prevent metal
forming the portion 4a for forming the neck from flowing to the
shoulder 3 or into the groove 10, which makes it possible to form
the groove 10 having a large depth and to prevent at least one of
the portion 4a and the body 2 from being wrinkled.
Further, since the line of the shoulder 3 is pressed to form the
groove 10, it is possible to form the groove 10 in a straight line
in the inclined direction of the shoulder 3.
In this way, it is possible to form the bottle-shaped can 1 having
a high-quality design.
Furthermore, since the width of the lower end 10e of the groove 10
gradually increases toward the lower end of the shoulder 3, it is
possible to reliably prevent metal forming the body 2 from flowing
to the shoulder 3 when the groove 10 is formed. In addition, since
the depth of the groove 10 gradually decreases toward the lower end
of the shoulder 3, that is, the displacement of the groove 10
decreases inward in the radial direction, it is possible to prevent
the upper end of the body 2 in the axial direction of the
cylindrical workpiece from being wrinkled in the axial direction
when the groove 10 is formed. The same effects as described above
are obtained from the upper end 10d of the groove 10. In
particular, in this embodiment, since the leading end 55b and the
rear end 55c of the pressure portion 55 of the mold 50 are formed
in triangular shapes, it is possible to reliably obtain the
above-mentioned effects.
In this embodiment, since the number of grooves 10 is in the range
of 8 to 22 and the groove 10 is formed so as to satisfy the
above-mentioned Expression, it is possible to adjust the gap
between adjacent pressure portions 55 to a predetermined value in
the mold 50 and thus to adjust the deformation of the first convex
11 by the pressure portion 55 that is used to press the first
convex 11 to form the groove 10. Therefore, it is possible to form
the grooves 10 in the entire shoulder 3 in the axial direction of
the cylindrical workpiece and thus to form the top portions 10c
that sharply protrude. As a result, it is possible to reliably form
the bottle-shaped can 1 having a high-quality design.
Further, since the groove 10 is formed and then the second convex 7
is formed, the grooves 10 make it possible to correct the roundness
of the portion 4a for forming the neck, even when the roundness of
the portion 4a is lowered.
Furthermore, since the groove forming mold 50 is used to form the
grooves 10, it is possible to form a plurality of grooves 10 in the
entire circumferential surface of the shoulder 3 at once and thus
to improve productivity. In addition, since a uniform load can be
applied to the entire circumferential surface of the shoulder 3, it
is possible to minimize a reduction in the roundness of the portion
4a for forming the neck.
Further, since the grooves 10 are formed under the conditions of
the internal pressure in the range of 0.05 MPa to 0.70 MPa, it is
possible to reliably prevent the body 2 from being bent when the
grooves 10 are formed.
In this embodiment, ten types of bottle-shaped cans having
different grooves (that is, grooves having different values of n,
a1, a2, L2, and .theta.) are formed, and it is checked whether the
groove 10 is clearly viewed due to the steep side walls 10a and the
steep top portion 10c of the groove 10. FIG. 5 shows the check
results. As can be seen from FIG. 5, when the number of grooves 10
is in the range of 8 to 22, a bottle-shaped can having a
high-quality design is formed.
The technical scope of the invention is not limited to the
above-mentioned embodiment, but various modifications and changes
of the invention can be made without departing from the spirit and
scope of the invention. For example, in the above-described
embodiment, the grooves 10 are formed and then the second convex 7
is formed, but the invention is not limited thereto. After the
second convex 7 is formed, the first convex 11 will be pressed to
form the grooves 10. In this case, it is possible to improve the
rigidity of the portion 4a for forming the neck against pressure
applied when the grooves 10 are formed, and to prevent the
roundness of the portion 4a from being lowered when the grooves 10
are formed. In addition, even when pressure applied to the shoulder
3 is transmitted to the portion 4a during the formation of the
grooves 10, the second convex 7 makes it possible to prevent the
portion 4a from being wrinkled due to the transmitted pressure.
The first convex 11 may be formed at only the lower end of the
shoulder 3, but it may not be formed at the upper end of the
shoulder 3. Then, the first convex 11 formed at the lower end of
the shoulder 3 may be pressed inward in the radial direction to
form the grooves 10. That is, the first convex (a thick portion) 11
protruding outward from the cylindrical workpiece may be formed on
at least one of the upper end and the lower end of the shoulder 3,
and a line linking the upper end to the lower end of the shoulder 3
in the inclined direction may be pressed to the inside of the
cylindrical workpiece to form a plurality of grooves 10 extending
in the inclined direction in the circumferential direction of the
shoulder 3. In this case, the lower end of the line is pressed by
the leading end 55b (mold surface) having a triangular shape, with
one vertex of the leading end 55b (an intersection ridgeline
between the top portions 55a) disposed at the top of the lower end
of the line, and a point on the line where the first convex 11 is
disposed is pressed inward in the radial direction.
Further, in the above-described embodiment, as shown in FIG. 1A,
the first convex 11 protrudes in the radial direction from both the
shoulder 3 and the portion 4a for forming the neck, but the
invention is not limited thereto. For example, as shown in FIG. 11,
a connection portion 61a between the shoulder 3 and the portion 4a
for forming the neck may be recessed inward in the radial
direction, so that the upper end of the shoulder 3 in the axial
direction of the cylindrical workpiece protrudes outward in the
radial direction from the connection portion 61a. The upper end of
the shoulder 3 in the axial direction of the cylindrical workpiece
may be a first convex 61. In this case, similar to the
above-described embodiment, the first convex 61 may be pressed
inward in the radial direction to form the grooves 10.
* * * * *